In some of existing roll-playing fighting games for displaying a character of a game player and enemy characters and the like on a monitor screen, movements of the game player's feet are detected and the game player character on the monitor screen are so moved as to conform to the detected movements. There is also known a viewing point changing technique for displaying a simulated 3D car race image on a monitor screen provided before a game player seated on a car seat and changing a viewing point of a camera to a preset position according to the inclining movement to left or right or forward-bending movement of the upper half of the game player's body.
The latter viewing point changing technique, disclosed in Japanese Patent Publication Serial No. Hei 10-85451 for instance, is adapted to respond to the movements of the upper half of the game player's body seated on the seat, i.e. change an image when a preset viewing point is changed from a predetermined one to the another predetermined one selected from a plurality of predetermined viewing points. As the viewpoints were predetermined, the change from one to the other is carried out within the limited choices among the predetermined viewpoints. It is likely that the player can learn the pattern of changes in viewpoint so that he/she can predict the change pattern in viewpoint by playing the game several times, giving the player a monotonous feel towards viewpoint changes.